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Damp Proofing Question
Possible penetrating damp from boarded floor void
Hello, looking for any advice on an apparent damp penetration from beneath a suspended floor in a front bedroom of a 1940 bungalow. We had a survey done by Rentokill about 3 years ago after we noticed mold on the corner of the external walls and a frequent musty smell. Rentokill said that there was no rising damp and that the mold was due to damp from the floor void entering the room because there was no DPM under the concrete slab that the sleeper walls and joists rested on. This seemed a good reason and they said the only way to stop the smell etc would be to concrete out the void, £2000, or place a DPM over the area and a scree. We decided to live with the smell, which depended largely on weather, and insulate the walls with polystyrene backed paper. The joists seemed fine at the time. We also lowered the outside ground level and gravelled it and added extra air brick to floor void just in case! All seemed fine until we recarpeted and I got a weather station, then I discovered that the humidity in the room was 65 to 70 % at 18°C and on pulling back the carpet the underlay was touch damp, as well as the floorboards, in that corner of the room where mold had previously grown. Thing is, can such a humidity be normally due to floor void penetrating damp or is there more going on here? Can the joists rot at this humidity?
There is mold on the window frames, as always, so condensation is an issue but not surprising at such humidity! The corner concerned is of two outside walls, one north facing, and the other walls are against a bedroom and hall, both of which have fully concreted floors.
Do you think we have another reason for this damp and level of humidity? Ideas very gratefully received!!
Hi it sounds like you do have a problem with humidity from below the floor boards if you have checked out the possibility of rising damp. Hard to tell without taking a look. Anything over 20% moisture will be ideal humidity to cause rot in timber. It sounds like you need a dpc installing.
Answered 9th Jan 2016